The present invention relates generally to optical detection systems, and in particular to a system and method for detecting contamination of a window of an optical detection system.
Aircraft systems often include, for example, icing detection systems such as those described in U.S. Pat. No. 7,986,408. These systems may send out, for example, a pulsed laser beam with a selected polarization. The beam is projected out of the aircraft and into, for example, a cloud. A receiver lens receives backscatter of the beam from the cloud and utilizes a plurality of high sensitivity photodetectors to sense the backscatter of the beam. The sensed backscatter may be interpreted to determine, for example, an icing condition.
The pulsed laser beam of these systems may be provided to the cloud through, for example, a window. These windows are subject to the accumulation of contaminants which can degrade optical transmission and compromise the quality of the measurements. It is desirable to provide continuous and autonomous detection of window contamination in order to alert aircraft personnel of the loss of data integrity and the need for manual cleaning of the window.
In aircraft icing conditions detection systems, it is aerodynamically desirable for the entire system to be flush-mounted with the skin of the aircraft. Prior art systems, such as those described in U.S. Pat. Nos. 7,948,628 and 8,320,424, implement window cleanliness detectors. These systems, however, include components located on an external side of the window. For example, an external mirror may be mounted outside the window to reflect the beam back through the window into a cleanliness detector. Components external to the window eliminate the aerodynamic advantages of a flush-mounted optical detection system.